Medusa System Added

Read about the medusa system [here](https://nadekobot.readthedocs.io/en/latest/medusa/creating-a-medusa/)

src/Nadeko.Medusa/Strings/LocalMedusaStringsProvider.cs

@@ -0,0 +1,40 @@
+namespace Nadeko.Snake;
+
+public class LocalMedusaStringsProvider : IMedusaStringsProvider
+{
+    private readonly StringsLoader _source;
+    private IReadOnlyDictionary<string, IReadOnlyDictionary<string, string>> _responseStrings;
+    private IReadOnlyDictionary<string, IReadOnlyDictionary<string, CommandStrings>> _commandStrings;
+
+    public LocalMedusaStringsProvider(StringsLoader source)
+    {
+        _source = source;
+        _responseStrings = _source.GetResponseStrings();
+        _commandStrings = _source.GetCommandStrings();
+    }
+
+    public void Reload()
+    {
+        _responseStrings = _source.GetResponseStrings();
+        _commandStrings = _source.GetCommandStrings();
+    }
+    
+
+    public string? GetText(string localeName, string key)
+    {
+        if (_responseStrings.TryGetValue(localeName.ToLowerInvariant(), out var langStrings)
+            && langStrings.TryGetValue(key.ToLowerInvariant(), out var text))
+            return text;
+
+        return null;
+    }
+
+    public CommandStrings? GetCommandStrings(string localeName, string commandName)
+    {
+        if (_commandStrings.TryGetValue(localeName.ToLowerInvariant(), out var langStrings)
+            && langStrings.TryGetValue(commandName.ToLowerInvariant(), out var strings))
+            return strings;
+    
+        return null;
+    }
+}